In U.S. Pat. No. 4,575,005 issued Mar. 11, 1986, the present inventor provides a boom arrangement in which a hose is mounted on a swivel mount at the ceiling which rotates about a vertical axis and carries the hose in a generally horizontal plane on a spring support which allows the hose end spaced outwardly from the swivel mount to be pulled downwardly from the horizontal plane for use.
U.S. Pat. No. 4,456,177 issued Jun. 26, 1984 to Johnson shows a cam in a horizontal plane where the cam follow is spring biased against the outside surface of the cam and the cam has a shape which is generally circular with a cut off section along a chord of the circle which tends to move the boom to a parked position. This arrangement has no parking effect around a majority of the circle and a relatively low parking force to a specific park position.
U.S. Pat. No. 5,620,157 to Titzer issued 1997 shows a first arrangement of double boom in which one boom remains in a horizontal plane underneath the other boom and the other boom twists up and down so that it is raised in the park position and twists downwardly rather than sliding downwardly as it passes underneath the first boom. This requires two different mounting arrangements for the two booms and apparently this was found unsatisfactory.
Turning therefore to U.S. Pat. No. 6,135,363 issued Oct. 24, 2000 to Titzer, in FIGS. 2 and 3 there is disclosed a twisted cam arrangement so that as the boom rotates it also moves vertically upwardly and downwardly on the sliding shaft. This arrangement uses vertical springs which pull the boom upwardly to the raised position so that this will act to rotate the boom to the raised position acting as a park position in which the boom extends away from the other of the booms.
It is desirable therefore to provide a self parking boom arrangement which locates the boom and hose at one side of the bay to allow the vehicle to enter and leave without engaging the hose and to allow the boom to be used with a second boom so that one is parked while the other is in use and can pass the first to swivel to a required location unimpeded.
Boom arrangements of this type generally mount the boom in a horizontal plane so that the hose can hang downwardly from the outer end of the boom and can be operated by the user by swiveling the boom around its vertical axis. However in some cases there is a pulling action downwardly on the boom either by a vigorous pulling action by the user or by the hose becoming entrapped and pulled. If there is no resilience in the system, any such pulling action can cause damage and breakage commonly at the center swivel location which is relatively complicated and therefore relative expensive.
In U.S. Pat. No. 4,131,132 (Zierden) issued Dec. 26, 1978 is disclosed a boom of this general arrangement where the inner end of the boom is mounted on a channel shaped support and is mounted for pivotal movement about a transverse horizontal axis at the channel member on trunions. A U-shaped member engages over an innermost end of the boom beyond the trunions and carries compression springs which pull the U-shaped member downwardly to hold the innermost end horizontal. Downward pulling on the outer end of the boom therefore pulls the U-shape member upwardly. Two compression springs are mounted one on each at the legs of the U-shape member so that the legs and the springs extend downwardly below the channel member. The legs and springs are thus exposed below the system and thus must be relatively short since they would otherwise interfere with the clearance underneath the system.
In U.S. Pat. No. 4,998,693 of the present inventor is disclosed another arrangement for mounting the boom for a pivoting action downwardly from the nominally horizontal plane. This arrangement provides an inexpensive construction including one or a pair of spring wires which are looped around a horizontal axis to form a coil at the inner end and an outwardly extending portion connected to the coil. Downward pulling movement on the outwardly extending portion thus acts to torsion the coil.
Both of these arrangements have been relatively successful in the marketplace. The second arrangement provides an inexpensive simple construction. The first arrangement provides a more rugged more complex construction but has the disadvantage that the amount of movement is limited.